Medium fixing method and medium support apparatus

ABSTRACT

In a medium fixing method of fixing one or a plurality of mediums on a shaft while the one or plurality of mediums each having a circular opening portion in a substantially center are stacked and the shaft is inserted into the opening portions, the mediums are fixed to the shaft while the mediums into which the shaft is inserted are guided with a fluid.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a medium fixing method andmedium support apparatus and, more particularly, to a medium fixingmethod and medium support apparatus suitable for an apparatus forpositioning/fixing an information recording/reproducing medium such as ahard disk, optical disk, or optical card or a medium such as asemiconductor wafer to a shaft and rotating the medium at a high speedwhile reducing the axis deflection amount.

[0003] 2. Related Background Art

[0004]FIG. 7 is a sectional view of the main part of a conventionalmedium support apparatus. In the medium support apparatus shown in FIG.7, when a plurality of magnetic disks as mediums 101 are to be stackedon a shaft 103, ring-like spacers 102 are inserted between the mediums101, and the mediums 101 are fixed with a clamper 104 to keep themparallel. This arrangement mainly aims at suppressing axis deflection ofthe mediums 101 when the shaft 103 rotates. In addition, the mediums 101are alternately pressed against the shaft 103 to be fixed while the gapsbetween holes 101 a of the respective mediums and the shaft 103 aredistributed to an arbitrary virtual axis, thereby suppressing dynamicweight balance disturbance caused by slight gaps between innercircumferential surfaces 101 b of the mediums 101 and the shaft 103.

[0005] Recently, information recording apparatus have been required torecord large volumes of information, and there are increasing tendenciesto increase the recording density and rotational speed of recordingmediums in the apparatuses. In order to attain high recording densityand high rotational speed, a reduction in track pitch and strict trackpitch error control are required. To meet these requirements, anyeccentricity between each medium 101 and a driving shaft 7 must besuppressed as well as synchronous and asynchronous vibrations of thedriving shaft 7. As compared with the required track pitch precision,the standard diameter tolerance of the hole 101 a in the central portionof the medium 101 is very large. The eccentricity caused between thedriving shaft 7 or shaft 103 and the medium 101 makes it difficult toimprove the track pitch precision.

[0006] In addition, in rotating the medium 101, the dynamic weightbalance disturbance in the medium support apparatus including themediums 101 produces vibrations. At a high rotational speed, thisdisturbance vibrates not only the driving shaft 7 but also the magneticrecording converter such as a magnetic head through the base on whichthe motor (not shown) is fixed, interfering with high-precisionpositioning of these components. Furthermore, stacking many mediums 101makes it difficult to correct the eccentricity between each medium andthe shaft 103, and increases the dynamic weight balance disturbance inthe medium support apparatus.

[0007] As described above, the conventional medium support apparatusmainly aims at suppressing surface deflection of the mediums 101 in thehorizontal direction. However, no function of correcting theeccentricity of each medium and the dynamic weight balance of the mediumsupport apparatus is added to the apparatus. For this reason, themediums 101 are alternately pressed against the shaft 103, and the gapsbetween the inner circumferential surfaces 101 b of the respectivemediums 101 and the shaft 103 are distributed to an arbitrary virtualaxis, thus suppressing the dynamic weight balance disturbance. This,however, maximizes the gaps between the respective mediums 101 and theshaft 103, and the eccentricity value becomes ½ times the tolerance sizeof the hole 101 a in the central portion of each medium. Under thecircumstances, demands have arisen for a medium support apparatuscapable of positioning/fixing mediums while keeping dynamic weightbalance by correcting the eccentricity of each medium.

SUMMARY OF THE INVENTION

[0008] It is an object of the present invention to provide a mediumfixing method and medium support apparatus, which can reduce the axisdeflection amounts of mediums such as magnetic disks with respect to adriving shaft when one or a plurality of mediums are positioned/fixed ona shaft, and can accurately rotate/drive the mediums at high speed.

[0009] According to one aspect of the present invention, there isprovided a medium fixing method of fixing one or a plurality of mediumson a shaft while the one or plurality of mediums each having a circularopening portion in a substantially center are stacked and the shaft isinserted into the opening portions, comprising fixing the mediums to theshaft while guiding the mediums into which the shaft is inserted with afluid.

[0010] According to further aspect of the present invention, there isprovided a medium fixing method of fixing one or a plurality of mediumson a shaft while the one or plurality of mediums each having a circularopening portion in a substantially center are stacked and the shaft isinserted into the opening portions, comprising fixing the mediums to theshaft while performing position adjustment between the shaft and themediums by forming a fluid film between a side surface portion of theshaft and inner circumferential surfaces of the opening portions of themediums.

[0011] According to further aspect of the present invention, there isprovided a medium fixing method of fixing one or a plurality of mediumson a shaft while the one or plurality of mediums each having a circularopening portion in a substantially center are stacked and the shaft isinserted into the opening portions, comprising fixing the mediums to theshaft while performing position adjustment between the mediums and theshaft by preparing a guide around the mediums and forming a fluid filmbetween an inner surface portion of the guide and outer circumferentialsurfaces of the mediums.

[0012] According to further aspect of the present invention, theforegoing method further comprises inserting the shaft into the openingportions while the mediums are stacked with spacers being insertedtherebetween.

[0013] According to further aspect of the present invention, there isprovided a medium support apparatus comprising a function of stackingone or a plurality of mediums each having a circular opening portion ina substantially center, inserting a shaft into the opening portions ofthe mediums, inserting a porous material between a side surface portionof the shaft and inner circumferential surfaces of the opening portionsof the mediums, and adjusting gasp between the inner circumferentialsurfaces of the opening portions of the mediums and the shaft by forminga fluid film between a side surface portion of the shaft and the innercircumferential surfaces of the opening portions of the mediums, therebypositioning the mediums.

[0014] According to further aspect of the present invention, there isprovided a medium support apparatus comprising a function of stackingone or a plurality of mediums each having a circular opening portion ina substantially center, inserting a shaft into the opening portions ofthe mediums, fixing the mediums to the shaft, disposing a guide having acylindrical porous material having an opening with a diametersubstantially equal to an outer diameter of the mediums, and adjustinggaps between outer circumferential surfaces of the mediums and an innersurface of the guide by forming a fluid film between the inner surfaceof the guide and the outer circumferential surfaces of the mediums,thereby positioning the mediums.

[0015] According to further aspect of the invention, in the foregoingapparatus, the plurality of mediums are stacked with ring-like spacersbeing inserted between the respective mediums.

[0016] According to further aspect of the present inventions theforegoing apparatus further comprises fixing means for fixing themediums to the shaft.

[0017] Other features and advantages of the present invention will beapparent from the following description taken in conjunction with theaccompanying drawings, in which like reference characters designate thesame or similar parts throughout the figures thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate embodiments of theinvention and, together with the description, serve to explain theprinciples of the invention.

[0019]FIG. 1 is a sectional view showing the main part of a portion of amedium support apparatus according to the first embodiment of thepresent invention;

[0020]FIG. 2 is a sectional view showing the main part of a portion ofthe medium support apparatus according to the first embodiment of thepresent invention;

[0021]FIG. 3 is a sectional view showing the main part of a portion ofthe medium support apparatus according to the second embodiment of thepresent invention;

[0022]FIG. 4 is a graph showing the relationship between the gaps andthe repulsive forces in the medium support apparatus according to thepresent invention;

[0023]FIG. 5 is a graph for explaining the relationship between theweight balance and the axis deflection amount in the conventional mediumsupport apparatus;

[0024]FIG. 6 is a sectional view showing the main part of a mediumsupport apparatus according to the second embodiment of the presentinvention; and

[0025]FIG. 7 is a sectional view showing the main part of a conventionalmedium support apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] Preferred embodiments of the present invention will now bedescribed in detail in accordance with the accompanying drawings.

[0027] A medium support apparatus according to the first embodiment ofthe present invention will be described below with reference to FIGS. 1to 3.

[0028]FIG. 1 shows the state of the apparatus before mediums (magneticdisks) are stacked on a shaft 3. FIG. 2 is a schematic view showing astate wherein a plurality of magnetic disks as mediums 1 are stacked onthe shaft 3 in the apparatus shown in FIG. 1. FIG. 3 is a schematic viewshowing a state wherein a spindle motor 6 is fixed to the shaft 3 inFIG. 2.

[0029] This shaft 3 has a fitting hole 3 a in the center of the lowerportion. The shaft 3 can be rotated by the spindle motor 6 through abearing (not shown). This fitting hole 3 a is formed to position/fix theshaft 3 to a shaft 6 a of the spindle motor 6 without any eccentricity.A plurality of horizontal holes 3 b extend through the shaft 3 from itsside surface to the fitting hole 3 a because the hole 3 a is also usedto inject a fluid such as air to correct the eccentricity of each medium1. A porous material 5 serving as a fluid spouting hole member isforcibly fitted on the shaft 3. Since mediums 1 and spacers 2 arepositioned with reference to the porous material 5, the porous material5 is fixed to the shaft 3 without any eccentricity with respect to thefitting hole 3 a in the lower portion of the shaft 3.

[0030] When a plurality of mediums 1 are to be stacked, the ring-likespacers 2 are inserted between the mediums 1 to ensure gaps between therespective mediums. The parallelism between the mediums 1 is maintainedby the spacers 2, and the squareness with respect to a driving shaft 7is determined by a collar 3C of the lower portion of the shaft 3. Owingto the tolerance of a diameter (opening portion) 1 a of the hole in thecentral portion of the medium 1, there is no guarantee that the slightgaps between inner circumferential surfaces 1 b of the mediums 1 and theporous material 5 have become uniform at this time. A damper 4 is fittedon the shaft 3 to restrict upward movement of the mediums 1 from theshaft 3 with the weight. In this state, a fluid such as air is injectedinto the shaft 3 through the inner holes 3 a and 3 b at a predeterminedpressure. The injected fluid is discharged through the porous material 5to form a fluid film in the gaps between the inner circumferentialsurfaces 1 b of the mediums 1, the spacers 2, and the side surfaceportion of the shaft 3. With this operation, the inner circumferentialsurfaces of the mediums 1 are guided by the fluid to make the gapsbetween the mediums 1 and the shaft 3 uniform throughout thecircumference. In addition, while the gaps are kept uniform, the mediums1 and spacers 2 are fixed to the shaft 3 with screws or by pressing themwith other members by using the damper 4. The above operation makes itpossible to stack/fix the respective mediums 1 while maintaining theparallelism of the mediums 1 and suppressing the eccentricity betweenthe respective mediums 1 and the shaft 3.

[0031]FIG. 3 shows a state wherein a plurality of magnetic disks 1 areactually stacked and fixed on the spindle motor 6 by using this mediumsupport apparatus. Referring to FIG. 3, the medium support apparatus ispositioned/fixed to the shaft 6 a of the spindle motor 6 with thefitting hole 3 a of the apparatus without any eccentricity. As a means(fixing means) for fixing the medium support apparatus to the spindlemotor 6, a means for fixing the apparatus to the shaft 6 a with screwsor vacuum chucking by a spindle motor ground surface 6 b is available.

[0032] As described above, in the medium support apparatus according tothis embodiment, when a plurality of mediums 1 are to be stacked on theshaft, the porous material 5 is provided on the side surface portion ofthe shaft 3 to be inserted into the holes la in the central portions ofthe mediums 1. A fluid such as air is then injected into the holes 3 aand 3 b of the shaft 3, and the fluid is discharged through the porousmaterial 5 to form a fluid film between the gaps between the holes 1 ain the central portions of the mediums 1 and the shaft 3. The mediums 1are then positioned while the gaps between the holes 1 a in the centralportions of the mediums and the shaft 3 are kept uniform, and thecentral holes are positioned without any eccentricity with reference tothe shaft 3. When a plurality of mediums are to be stacked as well asone medium 1, the gaps between the spacers 2 and the shaft 3 arepositioned and fixed in the same manner as described above, and dynamicweight balance is maintained with respect to the rotation of the overallmedium support apparatus. FIG. 4 shows the relationship between therepulsive force of a fluid and the frictional force of a medium withrespect to the distance from the porous material 5, which are obtainedby calculation. This calculation is based on the assumption that theslight gap between the inner circumferential surface 1 b of the medium 1and the porous material 5 is 6 to 55 82 m. Referring to FIG. 4, therepulsive force of the fluid is larger than the frictional force of themedium up to a gap of about 45 μm. If, therefore, the gap is equal to orsmaller than this numerical value, the eccentricity of the medium can betheoretically adjusted.

[0033]FIG. 5 shows the measurement results on axis deflection amounts inthe medium support apparatus of the present invention, in which aplurality of magnetic disks are stacked on the shaft and rotated atvarious rotational speeds. For reference, similar measurement results inthe conventional medium support apparatus shown in FIG. 7 are alsoshown. According to the present invention, the axis deflection amountsare much smaller than those in the prior art.

[0034]FIG. 6 is a sectional view of the main part of the secondembodiment of the present invention. This embodiment differs from thefirst embodiment only in that one or a plurality of disk-like mediums 1each having a circular hole 1 a in a substantially central portion arestacked on, a shaft 3 is inserted into the opening portions of themediums 1 to fix the mediums 1 on the shaft, a cylindrical porous guide(porous material) 5 a having an opening portion with an inner diameteralmost equal to the outer diameter of the mediums 1 is provided, and afluid film is formed between the inner surface of the guide 5 a and theouter circumferential surfaces of the mediums 1 by using a fluid such asair, thereby positioning the mediums 1 and guide 5 a while making thegaps between the outer circumferential surfaces of the mediums 1 and theinner surface of the guide 5 a uniform.

[0035] According to the present invention, there is provided a mediumsupport apparatus which can reduce the axis deflection amounts ofmediums such as magnetic disks with respect to a driving shaft when oneor a plurality of mediums are positioned/fixed on a shaft, and canaccurately rotate/drive the mediums at high speed.

What is claimed is:
 1. A medium fixing method of fixing one or aplurality of mediums on a shaft while the one or plurality of mediumseach having a circular opening portion in a substantially center arestacked and the shaft is inserted into the opening portions, comprisingfixing the mediums to the shaft while guiding the mediums into which theshaft is inserted with a fluid.
 2. A medium fixing method of fixing oneor a plurality of mediums on a shaft while the one or plurality ofmediums each having a circular opening portion in a substantially centerare stacked and the shaft is inserted into the opening portions,comprising fixing the mediums to the shaft while performing positionadjustment between the shaft and the mediums by forming a fluid filmbetween a side surface portion of the shaft and inner circumferentialsurfaces of the opening portions of the mediums.
 3. A medium fixingmethod of fixing one or a plurality of mediums on a shaft while the oneor plurality of mediums each having a circular opening portion in asubstantially center are stacked and the shaft is inserted into theopening portions, comprising fixing the mediums to the shaft whileperforming position adjustment between the mediums and the shaft bypreparing a guide around the mediums and forming a fluid film between aninner surface portion of the guide and outer circumferential surfaces ofthe mediums.
 4. A method according to claim 1, further comprisinginserting the shaft into the opening portions while the mediums arestacked with spacers being inserted therebetween.
 5. A medium supportapparatus comprising a function of stacking one or a plurality ofmediums each having a circular opening portion in a substantiallycenter, inserting a shaft into the opening portions of the mediums,inserting a porous material between a side surface portion of the shaftand inner circumferential surfaces of the opening portions of themediums, and adjusting gasp between the inner circumferential surfacesof the opening portions of the mediums and the shaft by forming a fluidfilm between a side surface portion of the shaft and the innercircumferential surfaces of the opening portions of the mediums, therebypositioning the mediums.
 6. A medium support apparatus comprising afunction of stacking one or a plurality of mediums each having acircular opening portion in a substantially center, inserting a shaftinto the opening portions of the mediums, fixing the mediums to theshaft, disposing a guide having a cylindrical porous material having anopening with a diameter substantially equal to an outer diameter of themediums, and adjusting gaps between outer circumferential surfaces ofthe mediums and an inner surface of the guide by forming a fluid filmbetween the inner surface of the guide and the outer circumferentialsurfaces of the mediums, thereby positioning the mediums.
 7. Anapparatus according to claim 5, wherein the plurality of mediums arestacked with ring-like spacers being inserted between the respectivemediums.
 8. An apparatus according to claim 5, further comprising fixingmeans for fixing the mediums to the shaft.